The Research On Blended Combustion And Emissions Characteristics Of New Oxygenated Fuels In Internal Combustion Engines

In recent years,the energy crisis caused by the increasing depletion of traditional fossil fuels and the environmental pollution caused by automobile exhaust emissions are becoming more and more serious,which has attracted the attention of all countries in the world.In China,these two problems are becoming increasingly prominent.Energy conservation and emission reduction has become a consensus.In order to alleviate the shortage of traditional fossil energy and reduce vehicle exhaust emissions,many experts and scholars actively explore and develop new vehicle renewable alternative fuels.New oxygenated fuels have attracted their attention because of their wide sources,simple preparation process,clean combustion and renewability,and they can also be directly used as fuels of vehicle's internal combustion engine.At present,there are many researches on oxygenated fuels at home and abroad,but there are many kinds of oxygenated fuels which can be mixed with each other.According to the research status of combustion and emission characteristics of new oxygenated fuels at home and abroad,there is no relevant literature on the combustion,performance and emissions characteristics of gasoline blended with methanol,ethanol and n-butanol respectively,nor isopropanol-n-butanol-ethanol(IBE)in gasoline engines.As for combustion in gasoline blended with acetone-n-butanol-ethanol(ABE),the proportion of ABE components and the content of ABE in ABE-gasoline still have wider space and the existing literature on its emissions has not taken into account the characteristics of unrestricted emissions(benzene,toluene,ethylbenzene,xylene,etc.);There have been a number of literatures on gasoline blended with ABE,but there are few literatures on diesel blended with ABE.Finally,there is no literature on numerical simulation of combustion and emission characteristics of ABE-diesel blended fuel in diesel engines.The research contents of this dissertation are as follows:(1)The combustion and emission characteristics of methanol/ethanol/n-butanol-gasoline in a gasoline engine were studied.The results show that the combustion phase is earlier and more obvious with the increase of ethanol content,and the brake thermal efficiency decreases.Therefore,ignition should be delayed when using ethanol-gasoline.The brake specific fuel consumption is the lowest.CO emission increases with the increase of equivalence ratio,while decreases with the increase of equivalence ratio.UHC emission of n-butanol-gasoline is lower than that of pure gasoline,and NO_x emission of n-butanol-gasoline is lower;in n-butanol-gasoline,B30combustion phase is the earliest,effective thermal efficiency is lower,CO,UHC and NO_x emissions are lower.(2)The combustion and emission characteristics of ABE-gasoline in a gasoline engine were studied.The results show that the combustion of ABE-gasoline is earlier than that of ABE-gasoline,and the ignition delay and rapid combustion period are shorter and more obvious with the increase of ABE content.The BTE of ABE-20 is the highest with the increase of BTE and BSFC,and the BTE of ABE-20 was the highest with the increase of ABE content.UHC emission decreases slightly and NO_x emission decreases slightly and ABE60 is the least when CO emission decreases at moderate content and high content;acetaldehyde and 1,3-butadiene emissions increases,while benzene,toluene and xylene decreases when ABE content increases;the combustion phase of ABE(361)30 and ABE(631)30 is slightly earlier and slightly lagged than pure gasoline,respectively;BTE of ABE(361)30 and ABE(631)30 is higher than that of pure gasoline and ABE(631)30 is the highest;increasing the equivalence ratio will increase BSFC and decrease BTE;ABE(631)30 emits less CO,UHC and benzene than ABE(361)30 and pure gasoline,and ABE(361)30 emits less toluene,ethylbenzene and xylene.(3)Comparing the combustion and emission characteristics of IBE-gasoline in an SI engine,the results show that:with the increase of IBE content,the combustion advances;all kinds of emissions of IBE-30 are lower than that of pure gasoline;the combustion phase of IBE-gasoline is similar to that of other alcoholic gasoline;IBE-gasoline has the lowest brake specific fuel consumption and the highest brake thermal efficiency and IBE30 has the highest brake thermal efficiency among IBE-gasoline blends.IBE-gasoline has the lowest UHC emission and the lowest CO emission;the NO_x emissions of all alcoholic gasoline are close;the combustion of IBE9.5W0.5 and IBE9W1 is earlier and later than that of pure gasoline after mixing water with IBE 10;the brake thermal efficiency of IBE9W1 is higher than that of IBE9.5W0.5 and IBE10,while its brake specific fuel consumption and BTX emissions are lower than those of IBE9.5W0.5 and IBE10 respectively.Compared with pure gasoline,the comubustion phase of IBE9W1 is earlier in the lean and stoichiometric air-fuel ratio conditions,lags behind in the rich condition,and has higher brake thermal efficiency and UHC emissions,but lower CO,NO_x and BTX emissions;the combustion of IBE-gasoline is earlier than ABE-gasoline and pure gasoline,so its optimal ignition timing should be postponed;among all kinds of ABE-gasoline and IBE-gasoline blends,IBE30 and ABE30 have the highest brake thermal efficiency and the lowest CO emissions,IBE30 and ABE60 have the lowest UHC emissions,IBE60and ABE60 have the lowest NO_x emissions,IBE10 has slightly higher brake thermal efficiency and lower CO,UHC and NO_x emissions than ABE10,and IBE-gasoline has more application prospects than ABE-gasoline.(4)The combustion and emission characteristics of ABE-diesel in diesel engine were compared and simulated.The results show that the ignition time is prolonged and the combustion phase is delayed after adding ABE fuel into diesel engine;the brake thermal efficiency is improved,the effective power of diesel engine is slightly decreased;CO emission is reduced,while UHC emission is increased,NO_x emission is increased,while NO_x emission is increased;the soot particulate emission can be reduced by adjusting the injection time;the ABE-n-heptane semi-detailed chemical kinetic mechanism can simulate the combustion process of ABE-diesel in diesel engine and describe the temporal and spatial distribution of NO_x and soot emission accurately,which is in good agreement with the relevant experimental data.